1. Technical Field
The present invention relates to a dust-proof glass which is used for a projection-type display device or the like, and relates to an electro-optic device and a projection-type image display device using the same.
2. Related Art
An electro-optic device which includes a transmission-type liquid crystal panel is used for a projection-type display device or the like. In the projection-type display device, light which is transmitted through a transmission-type liquid crystal panel is projected onto a screen or the like by a projection lens. At this time, since a scratch on a light incident surface of the transmission-type liquid crystal panel, a dust stuck to the light incident surface, or the like is within a short distance of a liquid crystal in a focus state, they are projected onto the screen, causing deteriorating display quality. To reduce the effects of such scratch, dust or the like, a dust-proof glass is attached on the light incident surface of the transmission-type liquid crystal panel and the distance between the liquid crystal in a focus state and the dust is increased so that the focus position is displaced. As a result, the scratch, dust or the like is made difficult to see even when it is projected onto the screen or the like. In addition, a light shielding film is provided on the dust-proof glass to prevent light from being incident to the outside of a display range of the transmission-type liquid crystal panel. Accordingly, a structure that includes a configuration and a two-layer light-shielding film is known. (See Japanese Patent No. 3799829 (page 22, FIG. 14).) In this configuration, a light shielding film for the dust-proof glass is provided on a side of a liquid crystal light bulb side that serves as the transmission-type liquid crystal panel (hereinafter referred to as “the light emitting surface of the dust-proof glass”). The two-layer light-shielding film includes a reflective film which reflects incident light from the outside and an absorbing layer which absorbs light from the side of the liquid crystal light valve.
In the case where a reflective film is provided on the light emitting surface of the dust-proof glass, incident light is transmitted through a surface of the dust-proof glass and reaches the reflective film. A part of the incident light reflected by the reflective film travels to the surface of the dust-proof glass again. Reflection occurs again on the surface of the dust-proof glass, and then a part of the incident light travels to the transmission-type liquid crystal panel. The light, however, has an incident angle that is different from an incident angle of a normal light beam. Therefore, the light is reflected by the transmission-type liquid crystal panel so that it will become feedback light or stray light. As a result, deterioration of display quality such as deterioration of display contrast, display unevenness or the like is likely to occur.